Conventionally, various color image-forming methods employing electrophotographic processes have been known.
In the color image-forming method, it is required that the spectral reflection characteristics of a toner approach the ideal values; when toners are superimposed to form an image on a support, no upper layer toner shields the lower layer toner, and when an image formed on a transparent sheet (hereinafter referred to as OHT) for an overhead projector, the toner layer results in minimum light scattering and no variation in hue is caused.
Colorants employed for colored toners include pigments such as C. I. Pigment Yellow 12, C. I. Pigment Yellow 17, C. I. Pigment Yellow 185, etc. However, the transparency of the toner layer is degraded because these pigments are dispersed into a toner in the state of secondary aggregates of not less than 0.1 .mu.m.
In order to improve dispersibility, a method has been known in which a master-batch is prepared by, in advance, dispersing a high concentration pigment into a resin and employing such as the colorant. However, because the size of the primary particles of the pigment is not less than 0.1 .mu.m, it is impossible to disperse the pigment into particles smaller than that. On account of this, when an image is formed by superimposing two or more toners, the upper layer is inferior in toner transparency to result in shielding of the toner in the lower layer and a resulting decrease in the chroma. Furthermore, in the case of forming an image on an OHT, when a pigment is employed as a colorant, a decrease in the transparency and deterioration of the color reproduction are caused due to the above reasons.